Proteinuria causes progressive kidney disease by impairing autophagy

描述(申请人提供)：蛋白尿与进行性慢性肾脏疾病有关。众所周知，近端肾小管上皮细胞暴露于大量白蛋白会导致肾小管萎缩和纤维化。然而，白蛋白在这一过程中可能的致病作用尚未完全阐明。开发新的治疗工具来预防或减缓蛋白尿性慢性肾脏疾病的进展，需要清楚地了解蛋白尿对肾小管细胞功能的影响。我们认为PTEC暴露于白蛋白可以抑制自噬，自噬是一种关键的细胞功能，负责细胞大分子和细胞器的周转，包括功能障碍的线粒体。我们的假设是，白蛋白通过以下机制之一损害自噬：(A)刺激白蛋白受体介导的信号事件；(B)上调有效的自噬抑制因子mTOR；或(C)导致溶酶体功能障碍或抑制自噬-溶酶体融合，这反过来又抑制自噬。我们假设，通过白蛋白超载或击倒关键的自噬蛋白来抑制自噬的实验将导致功能障碍的线粒体积累，从而增加活性氧的产生。由此产生的氧化损伤增加了线粒体膜的通透性和去极化，并促进了线粒体内成分的泄漏，如细胞色素c和AIF，这是促进细胞死亡的促凋亡蛋白。在活体实验中，蛋白尿将与自噬、ROS产生、PTEC凋亡、肾小管萎缩、纤维化和器官功能相关。我们将使用Ins2Akita/，这是一种糖尿病小鼠模型，出现蛋白尿、间质纤维化、肾小管功能障碍和萎缩。我们还将测试自噬的药理上调是否能改善蛋白尿引起的近端小管的变化。通过研究损害自噬的可能的信号转导级联反应，这一建议将提高我们对白蛋白在蛋白尿状态中的致病作用的理解，白蛋白是进行性慢性肾脏疾病的既定原因，并将调查自噬刺激物在改善进行性器官衰竭中的新作用。掌握这项建议中提出的新原则和新技术对我的科学发展和未来的研究生产力是至关重要的。它们将补充我以前在实验室的经验，使我能够为一个独特的研究领域奠定基础，并帮助我为蛋白尿肾脏疾病领域的研究深度和广度做出重大贡献。我相信，NIH的这个导师奖将促进我的科学成熟，并使我过渡到一个使我在独立研究支持方面具有竞争力的水平。

DESCRIPTION (provided by applicant): Proteinuria is associated with progressive chronic kidney disease. It is well known that exposure of proximal tubular epithelial (PTEC) cells to large amounts of albumin leads to the development of tubular atrophy and fibrosis. However, the possible pathogenic role of albumin in this process has not been fully elucidated. Development of new therapeutic tools to prevent or slow the progression of proteinuric chronic kidney disease requires clear understanding of the effect of proteinuria on tubular cell function. We propose that exposure of PTEC to albumin inhibits autophagy, a critical cellular function responsible for turnover of cellular macromolecules and organelles, including dysfunctional mitochondria. Our hypothesis is that albumin impairs autophagy by one of the following mechanisms: (a) stimulating albumin receptor-mediated signaling events; (b) up-regulating mTOR, a potent autophagy inhibitor; or (c) causing lysosomal dysfunction or inhibition of autophagosomal-lysosomal fusion which, in turn, inhibits autophagy. We hypothesize that experimental inhibition of autophagy by albumin overload or by knockdown of crucial autophagic proteins will result in accumulation of dysfunctional mitochondria leading to increased production of reactive oxygen species. The resulting oxidative damage increases the permeability and depolarization of the mitochondrial membrane and facilitates the leakage of intramitochondrial components such as cytochrome c and AIF, pro-apoptotic proteins that promote cell death. In in vivo experiments, proteinuria will be correlated with autophagy, ROS production, PTEC apoptosis, tubular atrophy, fibrosis and organ function. We will use Ins2Akita/+, a diabetic mouse model that develops proteinuria, interstitial fibrosis, tubular dysfunction and atrophy. We will also test if pharmacologic up-regulation of autophagy ameliorates proteinuria-induced changes in the proximal tubule. By investigating the possible signal transduction cascades that impair autophagy, this proposal will improve our understanding of the pathogenic role of albumin in proteinuric states, an established cause of progressive chronic kidney disease, and will investigate the novel role of autophagy stimulators in ameliorating progressive organ failure. Mastering the new principles and techniques presented in this proposal is essential for my scientific development and future research productivity. They will complement my previous experiences in the lab, permit me to lay down the foundation of a unique area of research and help me make a significant contribution to the depth and breadth of research in the field of proteinuric kidney diseases. I believe that this NIH mentored award will promote my scientific maturity and allow me to transition to a level that will make me competitive for independent research support.